1. Field of the Invention
The present invention relates to multi-line wireless telephone systems and, in particular, to providing secure communications in a time-division multiplexed (TDM) wireless telephone system.
2. Description of the Related Art
The use of telephones and telephone systems, including wireless telephone systems, is widespread. In wireless telephone systems, a cordless or wireless telephone handset unit communicates via either analog or digital radio signals with a base unit, which is typically connected via a standard telephone line to an external telephone network. In this manner, a user may employ the wireless handset to engage in a telephone call with another user through the base unit and the telephone network.
Multi-line wireless telephone systems are in use in various situations, such as businesses with many telephone users. Such systems employ a handset that communicates with up to N handsets simultaneously, typically with digital communications schemes, such as a spread-spectrum, time division multiple access (TDMA). In a TDMA system, a single RF channel is used, and each handset transmits and receives data during a dedicated time slice or slot within an overall cycle or epoch. It is desirable to provide various features, such as private branch exchange (PBX) features and capabilities, in a multi-line wireless telephone system.
One problem that may be encountered in such situations is breach of security. For example, an unauthorized third party may use a xe2x80x9cbootlegxe2x80x9d wireless handset to communicate via the base unit. Without adequate security, these and other types of security breaches may occur.
European Pat. App. No. 0 034 998 (Philips N V), March 1989 describes a wireless telephone system in which a base station stores an assigned security address code for a plurality of handsets, and the handsets also store the code assigned to each handset and transmitted to the handset by the base unit during recharging. U.S. Pat. No. 5,625,888 (Rxc3xcther et al.), 29 Apr. 1997 describes a process for combining transmitting/receiving devices of a cordless communication system to form a communication unit U.S. Pat. No. 5,371,783 (Rose et al.), 6 Dec. 1994 describes a method for continually monitoring the status of an RF link. European Pat. App. No. 0 301 573 (Nippon Electric Co.), 1 Feb. 1989 describes registration of new cordless telephones to an existing system.
A wireless telephone system, having one or more wireless handsets and a base unit. Each handset has a handset transceiver, and the base unit has a base transceiver and a handset docking station, which has a wired interface. The base unit digitally communicates over an RF channel with a handset via its handset transceiver only if the handset has previously been initialized by the base unit. The handset is initialized via the wired interface when it is physically docked in the docking station.